The present invention relates generally to an apparatus which can be used when an interventional procedure is being performed in a stenosed or occluded region of a blood vessel to capture embolic material that may be created and released into the bloodstream during the procedure. The apparatus of the present invention is particularly useful when performing balloon angioplasty, stenting procedures, laser angioplasty or atherectomy in critical vessels, such as the carotid arteries, where the release of embolic debris into the bloodstream can occlude the flow of oxygenated blood to the brain or other vital organs. It is to be understood that the apparatus and method of this invention can be used in numerous other vascular interventional procedures.
Numerous procedures have been developed for treating occluded blood vessels to allow blood to flow without obstruction. Such procedures usually involve the percutaneous introduction of the interventional device into the lumen of the artery, usually through a catheter. One widely known and medically accepted procedure is balloon angioplasty in which an inflatable balloon is introduced within the stenosed region of the blood vessel to dilate the occluded vessel. The balloon catheter is initially inserted into the patient""s arterial system and is advanced and manipulated into the area of stenosis in the artery. The balloon is inflated to compress the plaque and press the vessel wall radially outward to increase the diameter of the blood vessel.
Another procedure is laser angioplasty which utilizes a laser to ablate the stenosis by super heating and vaporizing the deposited plaque. Atherectomy is yet another method of treating a stenosed blood vessel in which a cutting blade or other specialized burr is rotated to shave the deposited plaque from the arterial wall.
In another widely practiced procedure, the stenosis can be treated by placing a device known as a stent into the stenosed region to hold open and sometimes expand the segment or blood vessel or other arterial lumen. Stents are particularly useful in the treatment of repair of blood vessels after a stenosis has been compressed by percutaneous transluminal coronary angioplasty (PTCA), percutaneous transluminal angioplasty (PTA) or removal by atherectomy or other means. Stents are delivered in a compressed condition to the target site, and then are deployed at the target location into an expanded condition to support the vessel and help maintain it in an open position.
In the process of treating such blood vessels at the location of the lesions, embolization of plaque (embolic debris) may occur during the treatment. Detached from the lesion, the embolic debris enters the bloodstream and subsequently migrate through the patient""s vasculature. Larger embolic debris can obstruct a vessel and cause ischemia, apoptosis, or vessel necrosis.
To allow the use of more aggressive treatment of vascular lesions, procedures have also been developed for preventing embolic debris from flowing through the vessels with the blood. One approach which has been attempted is the cutting of any debris into minute sizes which pose little chance of becoming occluded in major vessels within the patient""s vasculature. However, it is often difficult to control the size of the fragments which are formed, and the potential risk of vessel occlusion still exists. Another approach involves the use of a vacuum catheter which provides temporary suction to capture and remove embolic debris from the bloodstream. However, the vacuum catheter may not remove all of the embolic material from the bloodstream, and the suction produced by the vacuum catheter could cause trauma to the patient""s vasculature.
Another technique involves the placement of a filter downstream from the treatment site to capture embolic debris before it reaches the smaller blood vessels downstream. The placement of a filter in the patient""s vasculature during treatment of the vascular lesion can reduce the movement of the embolic debris in the bloodstream. Such filters are usually delivered in a collapsed position through the patient""s vasculature and then are expanded once in place in the patient""s body vessel to trap the embolic debris. The filter can then be collapsed to remove the filter (with the trapped embolic debris) from the body vessel. However, there have been difficulties associated with filtering systems, such as during the expansion and collapsing of the filter within the body vessel. It is possible for some of the trapped embolic debris to escape from the filter as the filter is being collapsed and removed from the body vessel.
There is a need in the art for an apparatus and method which can be utilized to treat an occluded vessel and capture embolic material that may be formed during the vascular procedure. Such an apparatus and method should also prevent the embolic material from escaping from the filter during the time that the filter is being collapsed or removed from the blood vessel (e.g., the carotid arteries). Such an apparatus and method should be relatively easy and safe to deploy, and be easily removed from the vasculature with minimal adverse impact or immunological response to the patient.
The present invention is directed to embolic filtering apparatus. The embolic filtering apparatus comprises a plurality of arms having a proximal end, a distal end, and a first segment end between the proximal end and the distal end, and an expandable member located at the distal end of the plurality of arms, wherein inflating the expandable member causes the plurality of arms to move radially outward. An unidirectional barrier is attached to the plurality of arms to capture embolic material when the plurality of arms are moved radially outward by the expandable member. The unidirectional barrier allows embolic material to pass in the direction towards the filter, but not in the opposite direction.
In one aspect of the embolic filtering apparatus, a first filter is located at the proximal end of the plurality of arms; a second filter located at the first segment end of the plurality of arms; wherein the first filter has a larger porosity than the second filter such that the second filter is capable of screening smaller embolic material than the first filter, allowing embolic material to be captured between the first filter and the second filter.
In another aspect of the embolic filtering system, the unidirectional barrier is located at the proximal end of the plurality of arms such that the unidirectional barrier allows embolic material to pass in the direction toward the filter, but not in the opposite direction.
In yet another aspect of the embolic filtering system, the plurality of arms are composed of a memory metal having a memory position, and the memory position represents the plurality of arms collapsed toward one another along a longitudinal axis. In its memory position, the plurality of arms are relatively straight. The plurality of arms collapse toward one another when the expandable member is deflated. The plurality of arms can also have a thickness that is greater at the distal end than at the proximal end.
In another aspect of the embolic filtering system, the filters limit the radial movement of the plurality of arms when the expandable member is expanded. The filters can be coated with an anti-coagulant to minimize the potentiality of clot formation.
The method of using the embolic filter apparatus comprises the steps of inserting an embolic filter device into a vessel; advancing the embolic filter device to a position downstream of the lesion to be treated in the vessel; expanding a expandable member to move a plurality of arms radially outward and deploy an unidirectional barrier and a first filter; and capturing in the embolic filter device embolic material that may be produced during treatment of the lesion. In use, the unidirectional barrier allows embolic material to pass in the direction toward the first filter, and not in the opposite direction.
In another aspect of the method of using the embolic filter apparatus, a second filter, capable of screening smaller embolic material than the first filter, is also deployed when the expandable member is expanded to move the plurality of arms radially outward; and embolic material is captured between the deployed first and second filters.
In another aspect of the method of using the embolic filter apparatus, the plurality of arms is composed of a memory metal having a memory position, and the memory position represents the plurality of arms collapsed toward one another along a longitudinal axis.
It is to be understood that the present invention is not limited by the embodiments described herein. The present invention can be included on a guide wire, on the delivery catheter, or on a separate catheter. The present invention can also be used in arteries, veins, and other lumen in the body. Other features and advantages of the present invention will become more apparent from the following detailed description of the invention, when taken in conjunction with the accompanying exemplary drawings.